Some vehicles have a hatch door for access to the rear of the vehicle. This is a door which is raised and lowered by swinging or pivoting in the vertical direction and is also known as a lift gate as it is commonly used in vans and light goods vehicles to provide access to the cargo area of the vehicle. Manually operated lift gates have one or two struts with provide a spring force to assist opening. Power struts have an electric motor used to extend and retract the strut to open and close the lift gate.
China Patent Application No. 201010288083.0, discloses an electric drive mechanism for a power strut. This drive mechanism includes a driver sleeve and a lead screw sleeve. An electric motor and a planetary gear train are mounted in the driver sleeve. A lead screw and a spring are mounted in the lead screw sleeve. The electric motor includes a stator and a rotor. The stator includes an outer housing, permanent magnets mounted to an inner surface of the outer housing, and end covers disposed at opposite ends of the outer housing. The rotor includes a shaft, and a rotor core and a commutator fixed to the shaft. The shaft is supported by bearings fixed to the end covers, such that the rotor can rotate relative to the stator.
A shortcoming of the above configuration is that the diameter of the outer housing of the stator is limited to the inner diameter of the driver sleeve, which in turn, limits the diameter of the rotor. This places a limitation on the output power of the motor.